It has been 11 years since the United States began using missile-firing drones to attack Al Qaeda in Afghanistan, Pakistan, Yemen and Somalia. But only now are we beginning a full public debate on this new form of warfare, and it took the nomination of the Obama administration's drone czar, John Brennan, as director of the Central Intelligence Agency, to force it.

That's a good thing, if belated. The Senate Intelligence Committee's hearing last week on Brennan's confirmation prompted a modest measure of openness on the criteria the administration uses to order drone strikes. And it opened a broader debate: Are drone strikes against U.S. citizens legal? Are drone strikes in general good policy?

First, on the legal basis for drone strikes. Since 2011, when a U.S. drone killed Anwar Awlaki, a New Mexico-born Al Qaeda militant in Yemen, members of Congress and others have been demanding to know what rules the administration was using to determine who was put on the "kill list." Could the president order the killing of a U.S. citizen, even a member of Al Qaeda, without violating his constitutional right to due process?

Last week, a Justice Department "white paper" summarizing the rules was leaked to NBC News, providing the clearest explanation yet of the administration's legal reasoning.

Its principal argument was that Al Qaeda is at war with the U.S., which makes any active member of Al Qaeda — U.S. citizen or not — an enemy combatant, liable to attack at any time. Conservative critics sometimes charge that the Obama administration treats terrorism as a matter of law enforcement, not warfare, but neither the administration's words nor its actions support that complaint in this regard.

Still, the Justice Department paper said, an American citizen in Al Qaeda has some right to due process before the U.S. government kills him. Accordingly, the administration has put these limits on itself: "An informed, high-level official of the U.S. government" must determine that the targeted person "poses an imminent threat of violent attack against the United States" (the definition of "imminent" is broad) and that capturing the target isn't feasible.

Brennan, who has been pushing for clear rules, told the Senate committee that the administration takes those criteria seriously. The public should understand "the care we take, the agony we go through, to make sure we do not have any collateral injuries and deaths," he said.

None of the senators questioned his sincerity, but several senators still said they would feel better if an outside authority reviewed the intelligence community's targeting decisions. As former CIA Director Michael V. Hayden has noted, there's an anomaly in the law: The government has to go to court for the authority to wiretap a U.S. citizen in Al Qaeda, but not to kill him.

Sen. Dianne Feinstein (D-Calif.), the committee chairwoman, said she wants to consider setting up a similar system for targeted killing: a court that would scrutinize the "kill list" and provide an independent review of the targets.

Intelligence community lawyers I've talked with hate the idea — "Why on earth would you want to get a judge involved?" one asked — but for a nation founded on the notion of a separation of powers, the principle of outside review is sound.

Still, protecting the rights of U.S. citizens in Al Qaeda is only part of what is at stake; those cases are unusual. In the long run, a more important question may be whether the drone strikes, which have killed more than 3,000 people, are creating more enemies for the United States than they are eliminating.

Scholars who have studied the political effects of drone strikes in Pakistan and Yemen have argued that even well-targeted raids often claim innocent victims, and the result is a backlash against the U.S. Likewise, Hayden and retired Gen. Stanley A. McChrystal, the former U.S. commander in Afghanistan, have warned that too many drone attacks — in Pakistan, for example, where the CIA uses "signature strikes" against suspected militants without identifying them individually — can be a bad thing.

"What scares me about drone strikes is how they are perceived around the world," McChrystal told the Reuters news agency last month. "The resentment created by American use of unmanned strikes ... is much greater than the average American appreciates. They are hated on a visceral level, even by people who've never seen one or seen the effects of one."

During a hearing that lasted more than three hours, only one senator asked about that critical issue — a senior Republican, Susan Collins of Maine.

"If you looked at a map back in 2001, you would see that Al Qaeda was mainly in Afghanistan and Pakistan, and if you look at a map today, you would see Al Qaeda in all sorts of countries," Collins said. "If the cancer of Al Qaeda is metastasizing, do we need a new treatment?"

Brennan agreed that the possibility of a backlash against drone strikes was "something we have to be very mindful of," and that counter-terrorism strategy cannot depend solely on missile strikes. But he insisted that the critics are wrong and that populations terrorized by Al Qaeda "have welcomed the work that the U.S. government has done."

Congress hasn't shown much appetite for regulating the U.S. war against terrorism until now. That's partly because there's been little public pressure to do so; an ABC News-Washington Post Poll last year found that a whopping 79% of Americans approved of drone strikes, including against U.S. citizens.

The intelligence committees have monitored the drone war and concluded that it's being conducted with care — although, as Feinstein notes, the evidence has been shrouded in secrecy.

But Collins shined a light on a question that can be debated in public: Are drone strikes effective in the long run, or are they creating more enemies than they kill? That's a worthy target for Senate and House committees to go after.